A displacement field is an assignment of displacement vectors for all points in a region or body that is displaced from one state to another. A displacement vector specifies the position of a point or a particle in reference to an origin or to a previous position. For example, a displacement field may be used to describe the effects of deformation on a solid body. Before considering displacement, the state before deformation must be defined. It is a state in which the coordinates of all points are known and described by the function: where